Major omission: Does the business model make sense to you? More specifically: Is there a demand for the product? Are there competitors? If not, why not -- are

Major omission: Does the business model make sense to you? More specifically: Is there a demand for the product? Are there competitors? If not, why not -- are you sure the product is actually something that somebody wants? If there are competitors -- how will your startup compete with them? Do you trust the people running the company to guide it to success, either directly, or because they have plans to hire people who can? Is the technology feasible, or are the founders embarking on an R&D project? There are no guarantees of course, and you can learn a lot and have fun at a startup that fails, but do your best to join with your eyes wide open.